In the US, opioid abuse is a significant public health issue. While treatments for opioid abuse are available, these programs often suffer high dropout rates. Published in the journal ACS Chemical Neuroscience, a new study led by Kathryn A. Cunningham (a professor of pharmacology and Director of the Center for Addiction Research in the University of Texas Medical Branch at Galveston) has suggested that the prescription weight-loss drug lorcaserin has the potential to be used as a new treatment for opioid use disorder.
An opioid is a substance that attaches itself to opioid receptors in parts of the brain that control pain and emotion. Common examples of this include, heroin, morphine and even over-the-counter prescription pain relievers such as oxycodone, codeine and fentanyl. While responsible for reducing pain, opioids also heighten feelings of euphoria and relaxation, which is why opioid pain relievers are often abused.
On an average day in the US, there are more than 650,000 prescriptions for opioid pain relievers dispensed. Approximately 3,900 people use these for non-medical purposes. In fact, the Centers for Disease Control and Prevention (CDC) estimate that more than three out of five deaths from drug overdose involve an opioid. In 2014 alone, deaths from drug overdoses involving opioids totaled more than 28,000.
Traditional opioid abuse treatments are plagued by high relapse rates, and reduce feelings of euphoria when using a particular drug. These treatments also fail to address “cue reactivity;” the powerful effect that a familiar drug-taking environment can exert on anticipation of the drug experience.
More often than not, cue reactivity plays an integral role in instances of relapse. Examples of cues include people, places, situations or equipment individuals associate with their opioid use.
In their study, researchers permitted rats to self-administer oxycodone while being exposed to a particular pattern of lights and sounds to create a specific drug-taking environment. After the rats became accustomed to administering the oxycodone, researchers removed their supply. The rats were then re-exposed to their familiar drug-taking environment with a test group receiving a dose of lorcaserin.
Lorcaserin is typically prescribed for weight loss as it affects the sensation of “fullness” by altering the brain’s serotonin system. By using an alternative pathway involving serotonin 2C receptors, serotonin also regulates the brain circuit which influences cue reactivity and drug reward.
When the rats were once again permitted to self-administer oxycodone, the rats that received the lorcaserin not only took less oxycodone, but reacted significantly less to the cues of the drug-taking environment.
In order to confirm the effect was caused by the lorcaserin, the researchers gave a group of rats lorcaserin alongside a drug which negates its effect by denying access to serotonin 2C receptors. The rats that received this drug combination then “tried very hard” to self-administer the oxycodone.
Based on the findings of this study, lorcaserin appears to not only reduce the craving to administer oyxcodone, but also the cue reactivity associated with relapse. Further studies are planned for drugs like lorcaserin to determine their usefulness for treatment of opioid addiction.
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